Multi-link new radio (NR)-physical downlink control channel (PDCCH) design

ABSTRACT

Aspects of the present disclosure relate to wireless communications and, more particularly, multi-link PDCCH monitoring. A UE may receive signaling configuring it to operate in at least one of a set of different modes of monitoring beam-pair links, wherein each beam-pair link comprises a transmit beam configured to be used by a base station (BS) for beamformed transmissions and a corresponding receive beam used by the UE. The UE may monitor at least two or more beam-pair links for downlink control channel transmissions based, at least in part, on the received signaling, and may transmit feedback to the BS based, at least in part, on the monitored beam-pair links.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/451,637, entitled “MULTI-LINK NR-PDCCH DESIGN,” filed on Jan. 27,2017, which is expressly incorporated herein by reference in itsentirety.

INTRODUCTION

Aspects of the present disclosure generally relate to wirelesscommunication and, more particularly, to multi-link New Radio(NR)-physical downlink control channel (PDCCH) design, wherein a UE isconfigured to operate in at least one of a set of different modes formonitoring beam-pair links.

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency divisional multiple access (SC-FDMA) systems,and time division synchronous code division multiple access (TD-SCDMA)systems.

In some examples, a wireless multiple-access communication system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple communication devices, otherwise known asuser equipment (UEs). In LTE or LTE-A network, a set of one or more basestations may define an eNodeB (eNB). In other examples (e.g., in a nextgeneration or 5G network), a wireless multiple access communicationsystem may include a number of distributed units (DUs) (e.g., edge units(EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs),transmission reception points (TRPs), etc.) in communication with anumber of central units (CUs) (e.g., central nodes (CNs), access nodecontrollers (ANCs), etc.), where a set of one or more distributed units,in communication with a central unit, may define an access node (e.g., anew radio base station (NR BS), a new radio node-B (NR NB), a networknode, 5G NB, gNB, gNodeB, etc.). A base station or DU may communicatewith a set of UEs on downlink channels (e.g., for transmissions from abase station or to a UE) and uplink channels (e.g., for transmissionsfrom a UE to a base station or distributed unit).

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is new radio (NR), for example, 5G radioaccess. NR is a set of enhancements to the LTE mobile standardpromulgated by Third Generation Partnership Project (3GPP). It isdesigned to better support mobile broadband Internet access by improvingspectral efficiency, lowering costs, improving services, making use ofnew spectrum, and better integrating with other open standards usingOFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink(UL) as well as support beamforming, multiple-input multiple-output(MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in NR technology.Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “DETAILED DESCRIPTION” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects of the present disclosure generally relate toconfiguring the UE to operate in at least one of a set of differentmodes of monitoring beam-pair links, wherein each beam-pair linkcomprises a transmit beam configured to be used by a base station (BS)for beamformed transmissions and a corresponding receive beam used bythe UE. Corresponding a BS may configured the UE to operate in at leastone of a set of different modes. Advantageously, aspects describedherein increase robustness against beam pair link blocking by monitoringPDCCH on multiple beam-pair links.

Certain aspects of the present disclosure provide a method for wirelesscommunication by a user equipment (UE). The method generally includesreceiving signaling configuring the UE to operate in at least one of aset of different modes of monitoring beam-pair links, wherein eachbeam-pair link comprises a transmit beam configured to be used by a basestation (BS) for beamformed transmissions and a corresponding receivebeam used by the UE, monitoring at least two beam-pair links fordownlink control channel transmissions based, at least in part, on thereceived signaling, and transmitting feedback to the BS based, at leastin part, on the monitored beam-pair links.

Certain aspects of the present disclosure provide an apparatus forwireless communication that may be performed, for example, by a UE. Theapparatus generally includes means for receiving signaling configuringthe UE to operate in at least one of a set of different modes ofmonitoring beam-pair links, wherein each beam-pair link comprises atransmit beam configured to be used by a base station (BS) forbeamformed transmissions and a corresponding receive beam used by theUE, means for monitoring at least two beam-pair links for downlinkcontrol channel transmissions based, at least in part, on the receivedsignaling, and means for transmitting feedback to the BS based, at leastin part, on the monitored beam-pair links.

Certain aspects of the present disclosure provide an apparatus forwireless communication that may be performed, for example, by a UE. Theapparatus includes at least one processor and a memory coupled to the atleast one processor. The at least one processor is configured to receivesignaling configuring the UE to operate in at least one of a set ofdifferent modes of monitoring beam-pair links, wherein each beam-pairlink comprises a transmit beam configured to be used by a base station(BS) for beamformed transmissions and a corresponding receive beam usedby the UE, monitor at least two beam-pair links for downlink controlchannel transmissions based, at least in part, on the receivedsignaling, and transmit feedback to the BS based, at least in part, onthe monitored beam-pair links.

Certain aspects of the present disclosure provide a computer readablemedium for wireless communication by a UE having computer-executableinstructions stored thereon for receiving signaling configuring the UEto operate in at least one of a set of different modes of monitoringbeam-pair links, wherein each beam-pair link comprises a transmit beamconfigured to be used by a base station (BS) for beamformedtransmissions and a corresponding receive beam used by the UE,monitoring at least two beam-pair links for downlink control channeltransmissions based, at least in part, on the received signaling, andtransmitting feedback to the BS based, at least in part, on themonitored beam-pair links.

Certain aspects of the present disclosure provide an apparatus forwireless communication by a base station (BS). The method generallyincludes transmitting signaling configuring a user equipment (UE) tooperate in at least one of a set of different modes of monitoringbeam-pair links, wherein each beam-pair link comprises a transmit beamconfigured to be used by the BS for beamformed transmissions and acorresponding receive beam used by the UE, transmitting downlink controlchannel transmissions to the UE using at least two beam-pair links,receiving feedback from the UE based, at least in part, on the monitoredbeam-pair links, and communicating with the UE based, at least in part,on the received feedback.

Certain aspects of the present disclosure provide an apparatus forwireless communication that may be performed, for example, by a BS. Theapparatus generally includes means for transmitting signalingconfiguring a user equipment (UE) to operate in at least one of a set ofdifferent modes of monitoring beam-pair links, wherein each beam-pairlink comprises a transmit beam configured to be used by the BS forbeamformed transmissions and a corresponding receive beam used by theUE, means for transmitting downlink control channel transmissions to theUE using at least two beam-pair links, means for receiving feedback fromthe UE based, at least in part, on the monitored beam-pair links, andmeans for communicating with the UE based, at least in part, on thereceived feedback.

Certain aspects of the present disclosure provide an apparatus forwireless communication that may be performed, for example, by a BS. Theapparatus includes at least one processor and a memory coupled to the atleast one processor. The at least one processor is configured totransmit signaling configuring a user equipment (UE) to operate in atleast one of a set of different modes of monitoring beam-pair links,wherein each beam-pair link comprises a transmit beam configured to beused by the BS for beamformed transmissions and a corresponding receivebeam used by the UE, transmit downlink control channel transmissions tothe UE using at least two beam-pair links, receive feedback from the UEbased, at least in part, on the monitored beam-pair links, andcommunicate with the UE based, at least in part, on the receivedfeedback.

Certain aspects of the present disclosure provide a computer readablemedium for wireless communication by a UE having computer-executableinstructions stored thereon for transmitting signaling configuring auser equipment (UE) to operate in at least one of a set of differentmodes of monitoring beam-pair links, wherein each beam-pair linkcomprises a transmit beam configured to be used by the BS for beamformedtransmissions and a corresponding receive beam used by the UE,transmitting downlink control channel transmissions to the UE using atleast two beam-pair links, receiving feedback from the UE based, atleast in part, on the monitored beam-pair links, and communicating withthe UE based, at least in part, on the received feedback.

Other aspects, features, and embodiments of the present invention willbecome apparent to those of ordinary skill in the art, upon reviewingthe following description of specific, exemplary aspects of the presentinvention in conjunction with the accompanying figures. While featuresof the present disclosure may be discussed relative to certain aspectsand figures below, all embodiments of the present disclosure can includeone or more of the advantageous features discussed herein. In otherwords, while one or more aspects may be discussed as having certainadvantageous features, one or more of such features may also be used inaccordance with the various aspects of the disclosure discussed herein.In similar fashion, while exemplary aspects may be discussed below asdevice, system, or method aspects it should be understood that suchexemplary aspects can be implemented in various devices, systems, andmethods.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. The appended drawingsillustrate only certain typical aspects of this disclosure, however, andare therefore not to be considered limiting of its scope, for thedescription may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram illustrating an example logical architectureof a distributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 3 is a diagram illustrating an example physical architecture of adistributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 4 is a block diagram conceptually illustrating a design of anexample BS and UE, in accordance with certain aspects of the presentdisclosure.

FIG. 5 is a diagram showing examples for implementing a communicationprotocol stack, in accordance with certain aspects of the presentdisclosure.

FIG. 6A illustrates an example of a DL-centric subframe, in accordancewith certain aspects of the present disclosure.

FIG. 6B illustrates an example of an UL-centric subframe, in accordancewith certain aspects of the present disclosure.

FIG. 7 illustrates examples of multi-beam communication, in accordancewith certain aspects of the present disclosure.

FIG. 8 illustrates examples of beam blocking, in accordance with certainaspects of the present disclosure.

FIG. 9 illustrates example operations performed by a UE, in accordancewith certain aspects of the present disclosure.

FIG. 10 illustrates example operations performed, by a BS, in accordancewith certain aspects of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to a multi-link NR-PDCCHdesign. As will be described in more detail herein, a link may include abeam-pair. A beam-pair is made up of a transmit beam used by atransmitter and a receive beam used by the receiver to receive thetransmission from the transmitter.

In communication systems employing beams, a BS and UE may communicateover active beams. Active beams may be referred to as serving beams,reference beams, or quasi-colocated (quasi-colocation, QCL) beams.Stated otherwise, according to an example, active beams, serving beams,reference beams, and QCL beams may be used interchangeably. According toan example, QCL beams refer to transmissions using the same or similarbeamforming as active or serving beams for which the QCL beam serves asa reference. Accordingly, QCL beams experience similar channelconditions for the active or serving beams.

Two antenna ports are said to be quasi co-located if properties of thechannel over which a symbol on one antenna port is conveyed can beinferred from the channel over which a symbol on the other antenna portis conveyed. QCL supports beam management functionality includingdetermining/estimating spatial parameters, frequency/timing offsetestimation functionality including determining/estimating Doppler/delayparameters, and radio resource management (RRM) functionality includingdetermining/estimating average gain. A network (e.g., BS) may indicateto a UE that the UE's data and/or control channel may be transmitted inthe direction of a transmitted reference signal. The UE may measure thereference signal to determine characteristics of the data and/or controlchannel.

According to one example, the BS may configure a UE with four beams,each associated with a different direction and different beamidentification. The BS may indicate to the UE a switch from a currentactive beam to one of the four configured beams. Following a beam switchcommand, both the UE and BS may switch to a particular beam. When areference beam is QCL to data or control beams, the measurements the UEmakes associated with a reference signal transmitted on a reference beamapplies to the data or control channel, respectively. In this manner,the performance of the data or control channel may be measured usingquasi-colocated reference beams.

Single beam-pair links may not be robust to link blockage. When a linkis blocked, the UE may experience down time and may have to performresource-intensive RLF procedures when the single beam-pair link fails.Accordingly, aspects of the present disclosure provide methods for a UEto monitor multi-links for PDCCH. By monitoring more than one link, theUE may increase throughput when one link is blocked or experiences a lowsignal quality.

A millimeter-wave (mmWave) communications bring gigabit speeds tocellular networks, due to availability of large amounts of bandwidth.The unique challenges of heavy path-loss faced by millimeter-wavesystems necessitate new techniques such as hybrid beamforming (analogand digital), which are not present in 3G and 4G systems. Hybridbeamforming may enhance link budget/signal to noise ratio (SNR) that maybe exploited to improve wireless communication.

Spectrum bands in high frequencies (e.g., 28 GHz, may be referred to asmmWave) provide large bandwidths capable of delivering multi-Gbps datarates, as well as extremely dense spatial reuse which may increasecapacity. Traditionally, these higher frequencies were not robust enoughfor indoor/outdoor mobile broadband applications due to high propagationloss and susceptibility to blockage (e.g., from buildings, humans, andthe like).

Despite these challenges, at the higher frequencies, small wavelengthsenable a large number of antenna elements in a relatively small formfactor. Unlike microwave links, which may cast very wide footprints,reducing the achievable amount of reuse of the same spectrum within ageographical area, mmWave links cast very narrow beams. Thischaracteristic of mmWave may be leveraged to form directional beams thatmay send and receive more energy to overcome propagation and path losschallenges.

These narrow directional beams can also be utilized for spatial reuse.This is one of the key enablers for utilizing mmWave for mobilebroadband services. In addition, the non-line-of-site (NLOS) paths(e.g., reflections from nearby building) can have very large energies,providing alternative paths when line-of-site (LOS) paths are blocked.

With more antenna elements and narrow beams, it becomes increasinglyvital to transmit signals in the appropriate direction, in an effort tomaximize the received signal energy at the UE.

The techniques described herein may be used for various wirelesscommunication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asuniversal terrestrial radio access (UTRA), cdma2000, etc. UTRA includeswideband CDMA (WCDMA), time division synchronous CDMA (TD-SCDMA), andother variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network may implement a radio technology such asglobal system for mobile communications (GSM). An OFDMA network mayimplement a radio technology such as evolved UTRA (E-UTRA), ultra mobilebroadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM®, etc. UTRA and E-UTRA are part of universal mobiletelecommunication system (UMTS). 3GPP Long Term Evolution (LTE) andLTE-Advanced (LTE-A), in both frequency division duplex (FDD) and timedivision duplex (TDD), are new releases of UMTS that use E-UTRA, whichemploys OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA,UMTS, LTE, LTE-A and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB aredescribed in documents from an organization named “3rd GenerationPartnership Project 2” (3GPP2). The techniques described herein may beused for the wireless networks and radio technologies mentioned above aswell as other wireless networks and radio technologies, including NewRadio (NR) technologies. For clarity, certain aspects of the techniquesare described below for LTE/LTE-Advanced, and LTE/LTE-Advancedterminology is used in much of the description below. LTE and LTE-A arereferred to generally as LTE.

Some examples of UEs may include cellular phones, smart phones, personaldigital assistants (PDAs), wireless modems, handheld devices, tablets,laptop computers, netbooks, smartbooks, ultrabooks, medical device orequipment, biometric sensors/devices, wearable devices (smart watches,smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g.,smart ring, smart bracelet)), an entertainment device (e.g., a music orvideo device, or a satellite radio), a vehicular component or sensor,smart meters/sensors, industrial manufacturing equipment, a globalpositioning system device, or any other suitable device that isconfigured to communicate via a wireless or wired medium. Some UEs maybe considered evolved or enhanced machine-type communication (eMTC) UEs.MTC and eMTC UEs include, for example, robots, drones, remote devices,such as sensors, meters, monitors, location tags, etc., that maycommunicate with a base station, another device (e.g., remote device),or some other entity. A wireless node may provide, for example,connectivity for or to a network (e.g., a wide area network such asInternet or a cellular network) via a wired or wireless communicationlink.

It is noted that while aspects may be described herein using terminologycommonly associated with 3G and/or 4G wireless technologies, aspects ofthe present disclosure can be applied in other generation-basedcommunication systems, such as 5G and later.

An example of an emerging telecommunication standard is new radio (NR),for example, 5G radio access. It is designed to better support mobilebroadband Internet access by improving spectral efficiency, loweringcosts, improving services, making use of new spectrum, and betterintegrating with other open standards using OFDMA with a cyclic prefix(CP) on the downlink (DL) and on the uplink (UL) as well as supportbeamforming, multiple-input multiple-output (MIMO) antenna technology,and carrier aggregation.

Example Wireless Communications Network

FIG. 1 illustrates an example wireless communication network 100, inwhich aspects of the present disclosure may be practiced. Techniquespresented herein may be used monitoring multiple links for PDCCH.

For example, a UE 120 may monitor at least two beam-pair links fordownlink control channel transmissions based on a configuration. A BS110 (TRP) may configure the UE to operate in at least one of a set ofdifferent modes of monitoring beam-pair links. The UE may monitor atleast two beam-pair links and may transmit feedback to the BS. Inresponse, the BS and UE may communicate based, at least in part, on themonitored beam-pair links.

FIG. 1 illustrates an example wireless network 100 in which aspects ofthe present disclosure may be implemented. For example, the wirelessnetwork may be a new radio (NR) or 5G network or and LTE network.

As illustrated in FIG. 1, the wireless network 100 may include a numberof BSs 110 and other network entities. A BS may be a station thatcommunicates with UEs. Each BS 110 may provide communication coveragefor a particular geographic area. In 3GPP, the term “cell” can refer toa coverage area of a Node B and/or a Node B subsystem serving thiscoverage area, depending on the context in which the term is used. In NRsystems, the term “cell” and gNB, Node B, 5G NB, AP, NR BS, NR BS, orTRP may be interchangeable. In some examples, a cell may not necessarilybe stationary, and the geographic area of the cell may move according tothe location of a mobile base station. In some examples, the basestations may be interconnected to one another and/or to one or moreother base stations or network nodes (not shown) in the wireless network100 through various types of backhaul interfaces such as a directphysical connection, a virtual network, or the like using any suitabletransport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a frequencychannel, etc. Each frequency may support a single RAT in a givengeographic area to avoid interference between wireless networks ofdifferent RATs. In some cases, NR or 5G RAT networks may be deployed.

A BS may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a Closed Subscriber Group (CSG), UEs for users in the home,etc.). A BS for a macro cell may be referred to as a macro BS. A BS fora pico cell may be referred to as a pico BS. A BS for a femto cell maybe referred to as a femto BS or a home BS. In the example shown in FIG.1, the BSs 110 a, 110 b and 110 c may be macro BSs for the macro cells102 a, 102 b and 102 c, respectively. The BS 110 x may be a pico BS fora pico cell 102 x. The BSs 110 y and 110 z may be femto BS for the femtocells 102 y and 102 z, respectively. A BS may support one or multiple(e.g., three) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., a BS or a UE) and sends atransmission of the data and/or other information to a downstreamstation (e.g., a UE or a BS). A relay station may also be a UE thatrelays transmissions for other UEs. In the example shown in FIG. 1, arelay station 110 r may communicate with the BS 110 a and a UE 120 r inorder to facilitate communication between the BS 110 a and the UE 120 r.A relay station may also be referred to as a relay BS, a relay, etc.

The wireless network 100 may be a heterogeneous network that includesBSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc.These different types of BSs may have different transmit power levels,different coverage areas, and different impact on interference in thewireless network 100. For example, macro BS may have a high transmitpower level (e.g., 20 Watts) whereas pico BS, femto BS, and relays mayhave a lower transmit power level (e.g., 1 Watt).

The wireless network 100 may support synchronous or asynchronousoperation. For synchronous operation, the BSs may have similar frametiming, and transmissions from different BSs may be approximatelyaligned in time. For asynchronous operation, the BSs may have differentframe timing, and transmissions from different BSs may not be aligned intime. The techniques described herein may be used for both synchronousand asynchronous operation.

A network controller 130 may couple to a set of BSs and providecoordination and control for these BSs. The network controller 130 maycommunicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another, e.g., directly or indirectly via wirelessor wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless network 100, and each UE may be stationary or mobile. A UE mayalso be referred to as a mobile station, a terminal, an access terminal,a subscriber unit, a station, a Customer Premises Equipment (CPE), acellular phone, a smart phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet, a camera, a gaming device, a netbook, a smartbook, anultrabook, a medical device or medical equipment, a biometricsensor/device, a wearable device such as a smart watch, smart clothing,smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, asmart bracelet, etc.), an entertainment device (e.g., a music device, avideo device, a satellite radio, etc.), a vehicular component or sensor,a smart meter/sensor, industrial manufacturing equipment, a globalpositioning system device, or any other suitable device that isconfigured to communicate via a wireless or wired medium. Some UEs maybe considered evolved or machine-type communication (MTC) devices orevolved MTC (eMTC) devices. MTC and eMTC UEs include, for example,robots, drones, remote devices, sensors, meters, monitors, locationtags, etc., that may communicate with a BS, another device (e.g., remotedevice), or some other entity. A wireless node may provide, for example,connectivity for or to a network (e.g., a wide area network such asInternet or a cellular network) via a wired or wireless communicationlink. Some UEs may be considered Internet-of-Things (IoT) devices.

In FIG. 1, a solid line with double arrows indicates desiredtransmissions between a UE and a serving BS, which is a BS designated toserve the UE on the downlink and/or uplink. A dashed line with doublearrows indicates interfering transmissions between a UE and a BS.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, etc. Each subcarriermay be modulated with data. In general, modulation symbols are sent inthe frequency domain with OFDM and in the time domain with SC-FDM. Thespacing between adjacent subcarriers may be fixed, and the total numberof subcarriers (K) may be dependent on the system bandwidth. Forexample, the spacing of the subcarriers may be 15 kHz and the minimumresource allocation (called a ‘resource block’) may be 12 subcarriers(or 180 kHz). Consequently, the nominal FFT size may be equal to 128,256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20megahertz (MHz), respectively. The system bandwidth may also bepartitioned into subbands. For example, a subband may cover 1.08 MHz(i.e., 6 resource blocks), and there may be 1, 2, 4, 8 or 16 subbandsfor system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR.

NR may utilize OFDM with a CP on the uplink and downlink and includesupport for half-duplex operation using TDD. A single component carrierbandwidth of 100 MHz may be supported. NR resource blocks may span 12sub-carriers with a sub-carrier bandwidth of 75 kHz over a 0.1 msduration. In one aspect, each radio frame may consist of 50 subframeswith a length of 10 ms. Consequently, each subframe may have a length of0.2 ms. In another aspect, each radio frame may consist of 10 subframeswith a length of 10 ms, where each subframe may have a length of 1 ms.Each subframe may indicate a link direction (i.e., DL or UL) for datatransmission and the link direction for each subframe may be dynamicallyswitched. Each subframe may include DL/UL data as well as DL/UL controldata. UL and DL subframes for NR may be as described in more detailbelow with respect to FIGS. 6 and 7. Beamforming may be supported andbeam direction may be dynamically configured. MIMO transmissions withprecoding may also be supported. MIMO configurations in the DL maysupport up to 8 transmit antennas with multi-layer DL transmissions upto 8 streams and up to 2 streams per UE. Multi-layer transmissions withup to 2 streams per UE may be supported. Aggregation of multiple cellsmay be supported with up to 8 serving cells. Alternatively, NR maysupport a different air interface, other than an OFDM-based. NR networksmay include entities such CUs and/or DUs.

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed further below,the scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. Base stations arenot the only entities that may function as a scheduling entity. That is,in some examples, a UE may function as a scheduling entity, schedulingresources for one or more subordinate entities (e.g., one or more otherUEs). In this example, the UE is functioning as a scheduling entity, andother UEs utilize resources scheduled by the UE for wirelesscommunication. A UE may function as a scheduling entity in apeer-to-peer (P2P) network, and/or in a mesh network. In a mesh networkexample, UEs may optionally communicate directly with one another inaddition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, and a mesh configuration, a scheduling entity and one ormore subordinate entities may communicate utilizing the scheduledresources.

As noted above, a RAN may include a CU and DUs. A NR BS (e.g., gNB, 5GNode B, Node B, transmission reception point (TRP), access point (AP))may correspond to one or multiple BSs. NR cells can be configured asaccess cells (ACells) or data only cells (DCells). For example, the RAN(e.g., a central unit or distributed unit) can configure the cells.DCells may be cells used for carrier aggregation or dual connectivity,but not used for initial access, cell selection/reselection, orhandover. In some cases DCells may not transmit synchronizationsignals—in some case cases DCells may transmit SS. NR BSs may transmitdownlink signals to UEs indicating the cell type. Based on the cell typeindication, the UE may communicate with the NR BS. For example, the UEmay determine NR BSs to consider for cell selection, access, handover,and/or measurement based on the indicated cell type.

FIG. 2 illustrates an example logical architecture of a distributedradio access network (RAN) 200, which may be implemented in the wirelesscommunication system illustrated in FIG. 1. A 5G access node 206 mayinclude an access node controller (ANC) 202. The ANC may be a centralunit (CU) of the distributed RAN 200. The backhaul interface to the nextgeneration core network (NG-CN) 204 may terminate at the ANC. Thebackhaul interface to neighboring next generation access nodes (NG-ANs)may terminate at the ANC. The ANC may include one or more TRPs 208(which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs, orsome other term). As described above, a TRP may be used interchangeablywith “cell.”

The TRPs 208 may be a DU. The TRPs may be connected to one ANC (ANC 202)or more than one ANC (not illustrated). For example, for RAN sharing,radio as a service (RaaS), and service specific AND deployments, the TRPmay be connected to more than one ANC. A TRP may include one or moreantenna ports. The TRPs may be configured to individually (e.g., dynamicselection) or jointly (e.g., joint transmission) serve traffic to a UE.

The local architecture 200 may be used to illustrate fronthauldefinition. The architecture may be defined that support fronthaulingsolutions across different deployment types. For example, thearchitecture may be based on transmit network capabilities (e.g.,bandwidth, latency, and/or jitter).

The architecture may share features and/or components with LTE.According to aspects, the next generation AN (NG-AN) 210 may supportdual connectivity with NR. The NG-AN may share a common fronthaul forLTE and NR.

The architecture may enable cooperation between and among TRPs 208. Forexample, cooperation may be preset within a TRP and/or across TRPs viathe ANC 202. According to aspects, no inter-TRP interface may beneeded/present.

According to aspects, a dynamic configuration of split logical functionsmay be present within the architecture 200. As will be described in moredetail with reference to FIG. 5, the Radio Resource Control (RRC) layer,Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC)layer, Medium Access Control (MAC) layer, and a Physical (PHY) layersmay be adaptably placed at the DU or CU (e.g., TRP or ANC,respectively). According to certain aspects, a BS may include a centralunit (CU) (e.g., ANC 202) and/or one or more distributed units (e.g.,one or more TRPs 208).

FIG. 3 illustrates an example physical architecture of a distributed RAN300, according to aspects of the present disclosure. A centralized corenetwork unit (C-CU) 302 may host core network functions. The C-CU may becentrally deployed. C-CU functionality may be offloaded (e.g., toadvanced wireless services (AWS)), to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions.Optionally, the C-RU may host core network functions locally. The C-RUmay have distributed deployment. The C-RU may be closer to the networkedge.

A DU 306 may host one or more TRPs (edge node (EN), an edge unit (EU), aradio head (RH), a smart radio head (SRH), or the like). The DU may belocated at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of the BS 110 and UE 120illustrated in FIG. 1, which may be used to implement aspects of thepresent disclosure. The BS may include a TRP or a gNB. One or morecomponents of the BS 110 and UE 120 may be used to practice aspects ofthe present disclosure. For example, antennas 452, Tx/Rx 454, processors466, 458, 464, and/or controller/processor 480 of the UE 120 and/orantennas 434, Tx/Rx 432, processors 420, 430, 438, and/orcontroller/processor 440 of the BS 110 may be used to perform theoperations described herein and illustrated with reference to FIGS.9-10. One or more of the components of the UE 120 and the BS 400 may beconfigured to perform means corresponding to the methods describedherein.

FIG. 4 shows a block diagram of a design of a BS 110 and a UE 120, whichmay be one of the BSs and one of the UEs in FIG. 1. For a restrictedassociation scenario, the base station 110 may be the macro BS 110 c inFIG. 1, and the UE 120 may be the UE 120 y. The base station 110 mayalso be a base station of some other type. The base station 110 may beequipped with antennas 434 a through 434 t, and the UE 120 may beequipped with antennas 452 a through 452 r.

At the base station 110, a transmit processor 420 may receive data froma data source 412 and control information from a controller/processor440. The control information may be for the Physical Broadcast Channel(PBCH), Physical Control Format Indicator Channel (PCFICH), PhysicalHybrid ARQ Indicator Channel (PHICH), Physical Downlink Control Channel(PDCCH), etc. The data may be for the Physical Downlink Shared Channel(PDSCH), etc. The processor 420 may process (e.g., encode and symbolmap) the data and control information to obtain data symbols and controlsymbols, respectively. The processor 420 may also generate referencesymbols, e.g., for the PSS, SSS, and cell-specific reference signal(CRS). A transmit (TX) multiple-input multiple-output (MIMO) processor430 may perform spatial processing (e.g., precoding) on the datasymbols, the control symbols, and/or the reference symbols, ifapplicable, and may provide output symbol streams to the modulators(MODs) 432 a through 432 t. Each modulator 432 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator 432 may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. Downlink signals from modulators 432 a through 432 tmay be transmitted via the antennas 434 a through 434 t, respectively.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) 454 a through 454 r, respectively. Eachdemodulator 454 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 454 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 456 may obtainreceived symbols from all the demodulators 454 a through 454 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 458 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 120 to a data sink 460, and provide decoded control informationto a controller/processor 480.

On the uplink, at the UE 120, a transmit processor 464 may receive andprocess data (e.g., for the Physical Uplink Shared Channel (PUSCH)) froma data source 462 and control information (e.g., for the Physical UplinkControl Channel (PUCCH) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by thedemodulators 454 a through 454 r (e.g., for SC-FDM, etc.), andtransmitted to the base station 110. At the BS 110, the uplink signalsfrom the UE 120 may be received by the antennas 434, processed by themodulators 432, detected by a MIMO detector 436 if applicable, andfurther processed by a receive processor 438 to obtain decoded data andcontrol information sent by the UE 120. The receive processor 438 mayprovide the decoded data to a data sink 439 and the decoded controlinformation to the controller/processor 440.

The controllers/processors 440 and 480 may direct the operation at thebase station 110 and the UE 120, respectively. The processor 440 and/orother processors and modules at the base station 110 may perform ordirect, e.g., the execution of the functional blocks illustrated in FIG.10, and/or other processes for the techniques described herein and forthose illustrated in the appended drawings. The processor 480 and/orother processors and modules at the UE 120 may also perform or direct,e.g., the execution of the functional blocks illustrated in FIG. 9,and/or other processes for the techniques described herein and thoseillustrated in the appended drawings. The memories 442 and 482 may storedata and program codes for the BS 110 and the UE 120, respectively. Ascheduler 444 may schedule UEs for data transmission on the downlinkand/or uplink.

FIG. 5 illustrates a diagram 500 showing examples for implementing acommunications protocol stack, according to aspects of the presentdisclosure. The illustrated communications protocol stacks may beimplemented by devices operating in a in a 5G system. Diagram 500illustrates a communications protocol stack including a Radio ResourceControl (RRC) layer 510, a Packet Data Convergence Protocol (PDCP) layer515, a Radio Link Control (RLC) layer 520, a Medium Access Control (MAC)layer 525, and a Physical (PHY) layer 530. In various examples thelayers of a protocol stack may be implemented as separate modules ofsoftware, portions of a processor or ASIC, portions of non-collocateddevices connected by a communications link, or various combinationsthereof. Collocated and non-collocated implementations may be used, forexample, in a protocol stack for a network access device (e.g., ANs,CUs, and/or DUs) or a UE.

A first option 505-a shows a split implementation of a protocol stack,in which implementation of the protocol stack is split between acentralized network access device (e.g., an ANC 202 in FIG. 2) anddistributed network access device (e.g., DU 208 in FIG. 2). In the firstoption 505-a, an RRC layer 510 and a PDCP layer 515 may be implementedby the central unit, and an RLC layer 520, a MAC layer 525, and a PHYlayer 530 may be implemented by the DU. In various examples the CU andthe DU may be collocated or non-collocated. The first option 505-a maybe useful in a macro cell, micro cell, or pico cell deployment.

A second option 505-b shows a unified implementation of a protocolstack, in which the protocol stack is implemented in a single networkaccess device (e.g., access node (AN), new radio base station (NR BS), anew radio Node-B (NR NB), a network node (NN), or the like.). In thesecond option, the RRC layer 510, the PDCP layer 515, the RLC layer 520,the MAC layer 525, and the PHY layer 530 may each be implemented by theAN. The second option 505-b may be useful in a femto cell deployment.

Regardless of whether a network access device implements part or all ofa protocol stack, a UE may implement an entire protocol stack (e.g., theRRC layer 510, the PDCP layer 515, the RLC layer 520, the MAC layer 525,and the PHY layer 530).

FIG. 6A is a diagram 600A showing an example of a DL-centric subframe.The DL-centric subframe may include a control portion 602. The controlportion 602 may exist in the initial or beginning portion of theDL-centric subframe. The control portion 602 may include variousscheduling information and/or control information corresponding tovarious portions of the DL-centric subframe. In some configurations, thecontrol portion 602 may be a physical DL control channel (PDCCH), asindicated in FIG. 6A. The DL-centric subframe may also include a DL dataportion 604. The DL data portion 604 may sometimes be referred to as thepayload of the DL-centric subframe. The DL data portion 604 may includethe communication resources utilized to communicate DL data from thescheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE).In some configurations, the DL data portion 604 may be a physical DLshared channel (PDSCH).

The DL-centric subframe may also include a common UL portion 606. Thecommon UL portion 606 may sometimes be referred to as an UL burst, acommon UL burst, and/or various other suitable terms. The common ULportion 606 may include feedback information corresponding to variousother portions of the DL-centric subframe. For example, the common ULportion 606 may include feedback information corresponding to thecontrol portion 602. Non-limiting examples of feedback information mayinclude an ACK signal, a NACK signal, a HARQ indicator, and/or variousother suitable types of information. The common UL portion 606 mayinclude additional or alternative information, such as informationpertaining to random access channel (RACH) procedures, schedulingrequests (SRs), and various other suitable types of information. Asillustrated in FIG. 6, the end of the DL data portion 604 may beseparated in time from the beginning of the common UL portion 606. Thistime separation may sometimes be referred to as a gap, a guard period, aguard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the subordinate entity (e.g., UE)) to UL communication(e.g., transmission by the subordinate entity (e.g., UE)). One ofordinary skill in the art will understand that the foregoing is merelyone example of a DL-centric subframe and alternative structures havingsimilar features may exist without necessarily deviating from theaspects described herein.

FIG. 6B is a diagram 600B showing an example of an UL-centric subframe.The UL-centric subframe may include a control portion 608. The controlportion 608 may exist in the initial or beginning portion of theUL-centric subframe. The control portion 608 in FIG. 6B may be similarto the control portion described above with reference to FIG. 6A. TheUL-centric subframe may also include an UL data portion 610. The UL dataportion 610 may sometimes be referred to as the payload of theUL-centric subframe. The UL portion may refer to the communicationresources utilized to communicate UL data from the subordinate entity(e.g., UE) to the scheduling entity (e.g., UE or BS). In someconfigurations, the control portion 608 may be a physical DL controlchannel (PDCCH).

As illustrated in FIG. 6B, the end of the control portion 608 may beseparated in time from the beginning of the UL data portion 610. Thistime separation may sometimes be referred to as a gap, guard period,guard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the scheduling entity) to UL communication (e.g.,transmission by the scheduling entity). The UL-centric subframe may alsoinclude a common UL portion 612. The common UL portion 612 in FIG. 6Bmay be similar to the common UL portion 606 described above withreference to FIG. 6A. The common UL portion 612 may additionally oralternatively include information pertaining to channel qualityindicator (CQI), sounding reference signals (SRSs), and various othersuitable types of information. One of ordinary skill in the art willunderstand that the foregoing is merely one example of an UL-centricsubframe and alternative structures having similar features may existwithout necessarily deviating from the aspects described herein.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including aconfiguration associated with transmitting pilots using a dedicated setof resources (e.g., a radio resource control (RRC) dedicated state,etc.) or a configuration associated with transmitting pilots using acommon set of resources (e.g., an RRC common state, etc.). Whenoperating in the RRC dedicated state, the UE may select a dedicated setof resources for transmitting a pilot signal to a network. Whenoperating in the RRC common state, the UE may select a common set ofresources for transmitting a pilot signal to the network. In eithercase, a pilot signal transmitted by the UE may be received by one ormore network access devices, such as an AN, or a DU, or portionsthereof. Each receiving network access device may be configured toreceive and measure pilot signals transmitted on the common set ofresources, and also receive and measure pilot signals transmitted ondedicated sets of resources allocated to the UEs for which the networkaccess device is a member of a monitoring set of network access devicesfor the UE. One or more of the receiving network access devices, or a CUto which receiving network access device(s) transmit the measurements ofthe pilot signals, may use the measurements to identify serving cellsfor the UEs, or to initiate a change of serving cell for one or more ofthe UEs.

Massive MIMO

Multiple-antenna (multiple-input multiple-output (MIMO)) technology isbecoming common for wireless communications and has been incorporatedinto wireless broadband standards such as long term evolution (LTE) andWi-Fi, for example. In MIMO, the more antennas the transmitter/receiveris equipped with, the more the possible signal paths (e.g., spatialstreams) and the better the performance in terms of data rate and linkreliability. Increased number of antennas can also involve increasedcomplexity of the hardware (e.g., number of radio frequency (RF)amplifier frontends) and increased complexity and energy consumption ofthe signal processing at both ends.

Massive MIMO may involve the use of a very large number of serviceantennas (e.g., hundreds or thousands) that can be operated coherentlyand adaptively. The additional antennas may help focus the transmissionand reception of signal energy into smaller regions of space. This canlead to huge improvements in throughput and energy efficiency, inparticularly when combined with simultaneous scheduling of a largenumber of user terminals (e.g., tens or hundreds). Massive MIMO can beapplied in time division duplex (TDD) operation and also in frequencydivision duplex (FDD) operation.

Example Multi-Link NR-PDCCH Design

In beamformed communication systems (including, for example, an mmWaveenvironment), a UE may be connected to a TRP via a particular beam. Whenthe single beam is blocked (e.g., due to a moving UE, human blocking orblocking/covering a portion of the UE), the UE may experience a radiolink failure (RLF). In an effort to minimize the time a UE has lost acontrol channel link and maximize throughput, it is desirable for PDCCHtransmissions to be robust against beam link blocking. Accordingly, theUE may be configured to monitor PDCCH on multiple beam links. Aspectsdescribed herein support PDCCH monitoring via multiple beam pair links.The multiple beams may be transmitted from a same or different TRP. Asingle beam-pair link may refer to a TX beam used by a transmitter totransmit a signal that is received by a receiver using a receive beam.

FIG. 7 illustrates examples 700 of multi-beam communication, accordingto aspects of the present disclosure. At 702, the UE receivestransmissions from two TRPs. The TRP 704 transmits a signal using atransmit beam (TX beam 1) and the UE uses a receive beam (RX beam 1) toreceive the signal. Similarly, the TRP 706 transmits a signal using atransmit beam (TX beam 2) and the UE uses a receive beam (RX beam 2) toreceive the signal. Accordingly, TX beam 1 and RX beam 1 comprise a beampair link (BPL, which may be referred to as a “link”) and TX beam 2 andRX beam 2 comprise another BPL.

At 702, the UE receives a first transmission from a first TRP 704 usinga first RX beam (RX beam 1), and the UE receives a second transmissionfrom a second TRP 706 using a second RX beam (RX beam 2). At 708, the UEreceives two beams from a single TRP 710 using two RX beams (RX beam 3and RX beam 4).

FIG. 8 illustrates examples 800 of beam blocking, according to aspectsof the present disclosure. FIG. 8 illustrates beam-pairs which make up aBPL (or link) between a TRP and a UE. As described above, with referenceto FIG. 7, a beam pair includes a transmit beam used by a transmitterand a corresponding receive beam used by the receiver. As an example,the transmit beam is used to transmit beamformed transmissions to thereceiver. The receiver uses a receive beam of the beam-pair link toreceive the transmitted signal.

At each of 802 and 804, one beam-pair link between a TRP and UE isblocked. For example, at 802, BPL 1 is blocked and at 804, BPL 2 isblocked. At 806, both of the beam-pair links (BPL and BPL2) are blocked.The one or more links may be blocked at 802, 804, and 806, for example,due to human blocking and/or a UE movement. While 802, 804, and 806illustrate two BPLs, more BPLs may be present between the TRP and theUE. When a link is blocked, it may be desirable for a UE to receivecontrol and/or data via another, non-blocked, link.

As described above, single beam-pair communication is not robust toblocking. The link may be lost for a long duration of time and mayrequire expensive RLF procedures to recover or establish a new link. TheRLF procedure may include searching for and connecting to a best beam.The down-time may be undesirable for a user.

According to aspects, semi-static signaling, such as RRC signaling, mayconfigure different one or more modes for NR-PDCCH beam-pair linkmonitoring. Based on the configured mode, the UE may monitor PDCCH in anNR environment.

For example in Mode 0, the UE may be configured to monitor PDCCHtransmitted on only one beam. Mode 0 may be a fallback or baseline mode.The time the control channel may be lost (T_(out)) may be quite high.When the single, monitored link is blocked, the UE may perform atime-intensive RLF procedure. The average throughput may not be veryhigh due to the significant throughput loss experienced when the singlelink is blocked. Because the UE is configured to monitor a single beam,advantageously, the signaling complexity may be very low.

In another mode, for example Mode 1, the UE may be configured by the TRPto monitor PDCCH/PDSCH in a hopping manner using pre-defined hoppingschedule. As an example, the UE may be configured to monitor PDCCH andPDSCH using a first beam during odd numbered slots and monitor PDCCH andPDSCH using another beam during even numbered slots. As another example,the UE may be configured with a hopping periodicity or configured toutilize a preconfigured hopping pattern. The UE may monitor PDCCH andPDSCH using a first beam on a first number of x slots and monitor PDCCHand PDSCH using a second beam on a number of y slots. According to thisexample, the PDCCH and PDSCH may be transmitted using the same beam.This is one example of the UE monitoring a downlink shared channel usinga same beam (beam-pair link) as a downlink control channel.

The beam hopping schedule may be a time division multiplexing (TDM) beamhopping schedule. In other words, in one time period (e.g., a slot), onebeam may be used to monitor PDCCH and in another time period (e.g.,slot), another beam may be used to monitor PDCCH transmissions.Similarly, the TDM beam hopping schedule may be used to monitor PDSCH inone time period and PDCCH in another time period.

In Mode 1, the UE may indicate to the TRP the preferred hopping pattern.A preferred hopping pattern may include the percentage of time a firsttransmit beam may be monitored for PDCCH/PDSCH and the percentage oftime a second transmit beam may be monitored by the UE for PDCCH/PDSCHreception.

For Mode 1, T_(out) is very low (as compared to Mode 0). Due to thehopping schedule, the UE may monitor a first beam and hop to a secondbeam. Even if the first beam is lost, the UE may receive signalstransmitted on the first beam when it hops back to the first beam fromthe second beam (e.g., in a later hop to the first beam). The averagethroughput may be low as compared to Mode 0, if one of the links isblocked. For example, due to the hopping schedule, the channel on onebeam may be strong; however, the UE may still hop to another beam whichmay be blocked, thereby reducing throughput. The signaling complexitymay be low, as the UE is configured to hop according to a predefinedpattern or schedule. Accordingly, Mode 1 may improve robustnessregarding link failure at the expense of throughput.

Monitoring Multiple BPLs

In another mode, for example, Mode 2, the UE may be configured tomonitor PDCCH using multiple BPLs. In one aspect (Mode 2A), the UE maybe configured to monitor beam-pairs in a TDM manner. For example, the UEmay be configured to monitor a first beam-pair in a first OFDM symbol,and the UE may be configured to monitor a second beam-pair in a secondOFDM symbol. According to aspects, the UE may be configured to monitormore than two beam-pairs. For example, the UE may be configured tomonitor any number of beam-pairs during a time period.

According to aspects, the TRP may configure the UE to measure a channelstate information reference signals (CSI-RS) port or a synchronizationsignal (SS) port that is QCL with the PDCCH demodulation referencesignal (DMRS) port.

In one aspect (Mode 2B), the UE may monitor different resource sets(different control subbands) in the same OFDM symbols. The UE maymonitor a first set of subbands for a first PDCCH on a first beam andmonitor a second set of subbands for a second PDCCH on a second beam.According to an aspect, the monitoring configuration may be specified ina controlled resource set. A first controlled resource set may include afirst set of frequency subbands and a second controlled resource set mayinclude a second set of frequency subbands. Each controlled resource setmay include resources which are contiguous in time but not in frequency.

In one aspect (Mode 2C), two or more TRPs may transmit a PDCCH using asame OFDM symbol and a same frequency resource set. The UE may beconfigured to monitor a first beam-pair link on an ODFM symbol from afirst TRP (e.g., BS) and monitor a second beam-pair link on the sameOFDM symbol from another TRP (e.g., BS). In one aspect (Mode 2D), twoTRPs may each transmit a PDCCH with different payloads and theircorresponding PDSCHs.

According to aspects, the UE may monitor one or more OFDM symbolsdepending on the configuration wherein different subsets of differentbeam pairs may occupy different frequency subbands in a configured OFDMsymbol. For instance, if one OFDM symbol is configured, beam 1 mayoccupy subband 1 and beam 2 may occupy subband 2. If two OFDM symbolsare configured, in OFDM symbol 1, subset 1 (or all bits) from beam 1 mayoccupy subband 1 and subset 2 (or all bits) from beam 2 may occupysubband 2 and in OFDM symbol 2, subset 1 (or all bits) from beam 2 mayoccupy subband 1 and subset 2 (or all bits) from beam 1 may occupysubband 2.

Generally, in Mode 2, the UE may be configured to monitor PDCCH onmultiple beam-pair links. The UE may feedback the beam-pair link(s) forwhich it was able to decode PDCCH from each TRP. In other words, the UEmay try to decode the PDCCH from each of the TRPs. The UE may determinethe BPL(s) on which it was able to decode the PDCCH and may feedbackthis information to the TRP. According to aspects, the UE may feedbackthe channel strength of the beam-pair links via an uplink channel suchas a PUCCH and/or PUSCH.

In addition to using the channel state information reference signals(CSI-RS) to determine channel strength measurements (which may depend onthe periodicity with which the UE is configured), demodulation referencesignals (DMRS) from the PDCCH may be used to determine channel strengthmeasurements. Using DMRS may allow for quicker channel strengthmeasurements by the UE. DMRS is just one example of a reference signalthat may be used in accordance with aspects of the present disclosure.Accordingly, any RS transmitted on the PDCCH may be used in accordancewith aspects describe herein. According to aspects, the UE may usemeasurement reference signals (MRS) and/or CSI-RS to estimate the bestbeam-pair link.

The UE's feedback to the TRP may indicate that one TX beam or both TXbeams are strong (e.g., SNR of the TX beam exceeds a threshold value).When both beams are strong, the TRP may use both beams simultaneouslyfor PDSCH (Rank 2 transmission). Based on the received feedback, the TRPmay serve the UE on a new beam. According to aspects, the TRP may servethe UE on either of the beams or both of the beams.

Assuming channel reciprocity, the UE may choose the appropriate beam totransmit feedback on the PUCCH. For example, assuming channelreciprocity and a strong DL DMRS (generally, DL RS) strength onbeam-pair 2 and a weak signal strength on beam-pair 1 (for example, dueto blocking), the UE may use the receive beam associated with beam-pair2 to transmit the channel feedback.

After the TRP receives feedback from the UE regarding the PDCCH, the TRPmay indicate a beam change for PDSCH transmission. According to anexample, the TRP may receive feedback in slot 1 that the signal strengthon beam 1 is weak and that the signal strength on beam 2 is strong. In asubsequent slot, for example, in slot 4, the TRP may configure/schedulethe UE with a beam ID the PDSCH will be transmitted on (beam ID of beam2). According to an example, the beam change may indicate a CSI-RS portwhich is QCL with the PDSCH transmission.

When there is no beam change, the PDSCH may be scheduled in a same slotas the PDCCH. In other words, the PDCCH and PDSCH may have same-slotscheduling.

When there is a beam change from the PDCCH to the PDSCH, the UE may needtime to determine which receive beam it should use to receive the PDSCH.The UE may have to decode the PDCCH and change its RX beam. Therefore,the PDCCH and PDSCH may be scheduled in different slots (cross-slotscheduling), in an effort to allow the UE to monitor and decode thePDCCH and determine which receive beam to use to receive the PDSCH thatis transmitted using a different beam than the PDCCH.

According to aspects, when there is a beam change from the PDCCH to thePDSCH, the PDCCH may schedule the PDSCH using cross-symbol scheduling.In cross-symbol scheduling, the PDCCH may schedule the PDSCH for a startsymbol occurring in the same slot as the PDCCH. In other words, the TRPmay introduce a guard symbol (or guard period) within the slot when thePDCCH indicates a beam direction change for PDSCH in a same slot. Theguard period may separate the downlink control transmission from thedownlink shared channel transmission. The PDSCH may be received atdifferent starting OFDM symbol in an effort to allow the UE to change areceive beam direction.

In one example of cross-symbol scheduling, the PDSCH may be transmittedin a later symbol of the same slot as compared to the regularlyscheduled PDSCH. For example, PDSCH may regularly be scheduled forsymbol 2. Due to cross-symbol schedule, the PDSCH may be received in alater symbol of the slot, for example, in OFDM symbol 7 instead ofsymbol 2. Thus, the PDSCH transmission is received in the same slot asthe PDCCH, but with a later PDSCH start symbol as compared to theregularly scheduled PDSCH transmission. Cross-symbol scheduling may beused for UEs, for example with high capabilities, which are able todecode control signals and switch its receive beam in a short time spanof a few OFDM symbols.

Mode 2A, Mode 2B, and Mode 2C may have a very low T_(out) as compared toMode 0. The T_(out) may be a function of feedback delay, which may beonly a few slots. The average throughput may be much higher than Mode 0and Mode 1, as the TRP quickly switches to a better beam (e.g., based onfeedback from the UE). If the UE feedback requests rank 2 (or higher)transmissions at high SNRs, the throughput may be higher than when theUE is served using one of the beams. The signaling complexity may bemoderate, as additional TRP resources may be needed to transmit multiplePDCCHs.

Mode 2A may be beneficial for a TRP with analog beamforming constraints(TRPs with sub-array architecture). Mode 2B may be beneficial for TRPswith a fully connected architecture.

Both Mode 2A and Mode 2B may increase the number of blind decodesperformed by the UE to monitor PDCCH. For example, in the TDM case ofMode 2A, the UE may monitor PDCCH from one directional beam in a firstsymbol. In the next symbol, the UE may monitor PDCCH from a differentdirectional beam. Assuming it takes 44 blind decodes to decode the PDCCHfrom the first directional beam in the first symbol and another 44 blinddecides to decode the PDCCH from the different directional beam in thenext symbol, the UE 88 blind decodes to decode the PDCCH. According toaspects, candidate restriction may be defined to reduce the number ofblind decodes. Instead of performing 44 blind decodes on the firstsymbol and 44 blind decodes on the next symbol, the UE may be configuredto perform 22 blind decodes on each symbol. In this manner, the numberof blind decodes may not increase and the UE may have the flexibility tomonitor two different beam-pairs. While the above example describes theUE monitoring two beam-pair links, aspects of the present disclosureapply to a UE monitoring more than two beam-pair links.

As described above, Mode 2A and Mode 2B, without candidate reduction,may increase a number of blind decodes performed by the UE. In Mode 2C,the number of blind decodes may be reduced by measuring the channelstrength of two or more beams simultaneously.

A first TRP may transmit a PDCCH using beam 0 from port 0. A second TRPmay transmit a PDCCH using beam 1 from port 1. Both TRPs may use thesame resource set (frequency resources) and the PDCCHs may have the samepayload. The DMRS of port 0 and 1 may be configured to apply orthogonalcovers or not.

In Mode 2C, the UE may perform channel estimation using port 0 and port1 as h₀ and h₁ respectively. The effective channel may be obtained ash₀+h₁. h₀ is a column vector if there are multiple Rx chains, and h₀ maybe a matrix, if PDCCH is transmitted from more than 1 transmit port.Blind decoding of PDCCH may be performed using the effective channel. Inthis way, the number of blind decodes has not increased. Instead, the UEhas performed two different channel estimates. As a byproduct of thisscheme, h₀ and h₁ may be used to measure and identify which beam isstronger, or determine both beams are strong (as in Rank 2 or higher)While the above example describes the UE monitoring two links, aspectsof the present disclosure apply to a UE monitoring more than two links.

Assuming channel reciprocity, using this measurement, the UE may selectthe uplink port/beam to use for PUCCH transmission. The PUCCH/PUSCHtransmission may be used to feedback the preferred DL beam. Based on thefeedback, the TRP may schedule the UE using the requested beam insubsequent transmissions.

DMRS Based Reporting

The TRP may configure to the UE to report the signal strength of certainDMRS transmitted in the PDCCH and/or PDSCH. Additionally oralternatively, the TRP may configure the measurementduration/periodicity and/or averaging duration across multiple DMRS.

UE may measure signal strength using only DMRS or using re-encoded data(PDCCH/PDSCH) after successful decoding. The UE may decide to use onlyDMRS and/or to use re-encoded data. Or, the TRP may configure the UE touse DMRS, re-encoded data, or both. In certain scenarios, the TRP mayallow the UE more time for measurements to facilitate the need to decodedata.

According to aspects, the UE may report slot indices over whichPDCCH/PDSCH were averaged, which may help tracking error events such asa missed PDCCH/PUCCH. For example, a TRP may believe the UE is in adiscontinuous transmission (DTX) mode; however, the TRP may havereceived a PUCCH grant from the UE. In this scenario, the TRP maymistakenly think the UE missed the PDCCH. However, a measurement reportfrom the UE sent on a subsequent PUCCH may alert the TRP of the mistake.

Configurations of Control and Data Beams

The TRP may configure UE to monitor N beams for control and M beam fordata, where N and M may be different integer values. The TRP canconfigure relationship between control and data beams.

For example in Mode 1, each control beam may be mapped to a data beam(each PDCCH may be mapped to a PDSCH). In Mode 2, the TRP may mapmultiple PDCCHs to one PDSCH or multiple PDCCHs to multiple PDSCHs.Accordingly, two control beams may be mapped to one data beam. As anexample, when two PDCCHs are mapped to one PDSCH, a control symbol maybe transmitted in a 1st OFDM symbol and the same control signal may betransmitted in a 2nd OFDM symbol using a different beam. The data may betransmitted on one beam in the 3rd-14th OFDM symbols using a singlebeam. In general, however, enabling robustness for data (e.g., bymapping multiple data beams to one control beam) may be an inefficientuse of time-domain resources.

According to aspects, the PDCCH from each of the beam-pair links may bedifferent. As an example, a PDCCH/PDSCH transmitted using one beam maybe different than PDCCH/PDSCH transmitted using another beam. This mayminimize backhaul signaling between the BSs. In some aspects, forexample, when backhaul signaling between the TRPs is not a constraint,two or more different PDCCHs may be accommodated with a single PDCCH andsingle PDSCH (higher rank).

According to aspects, the BS may switch or change a transmit beam (for(example a downlink control beam). The BS may transmit an indication forthe UE to monitor a different beam, for example, based on receivedfeedback from the UE. Based on an RRC configuration, the UE may switchto monitoring the updated transmit beam N slots after receiving theindication of the change in transmit beam. The UE may transmit aconfirmation of the beam change. The confirmation may be an explicitacknowledgement.

According to aspects, the BS may transmit an indication of a beam switchand a grant scheduling a PDSCH. The UE may decode the data and transmitan acknowledgment (or negative acknowledgement). The acknowledgement (ornegative acknowledgement) of the PDSCH may provide confirmation that theUE received the indication of the beam switch and the grant.Accordingly, an acknowledgement or negative acknowledgment for the PDSCHmay provide confirmation for the beam change and reception of thedownlink signaling. In this manner, the acknowledgment for a beam changemay implicit via the explicit PDSCH acknowledgment (or negativeacknowledgement).

FIG. 9 illustrates example operations 900 which may be performed by a UE120 having one or more components as illustrated in FIG. 4, in an effortto monitor multiple beam-pair links for a downlink control channeltransmission.

At 902, the UE may receive signaling configuring the UE to operate in atleast one of a set of different modes of monitoring beam-pair links,wherein each beam-pair link comprises a transmit beam configured to beused by a base station (BS) for beamformed transmissions and acorresponding receive beam used by the UE.

The UE may receive signaling configuring the UE to monitor the at leasttwo beam-pair links for the downlink control channel transmissions basedon a frequency hopping schedule. The UE may monitor a downlink sharedchannel using a same beam-pair link as the downlink control channel.

Additionally or alternatively, the UE may receive signaling configuringthe UE to monitor a first beam-pair link in a first orthogonalfrequency-division multiplexing (OFDM) symbol and to monitor a secondbeam-pair link in a second OFDM symbol.

Additionally or alternatively, the UE may receive signaling configuringthe UE to monitor a first beam-pair link in a first set of frequencysubbands and to monitor a second beam-pair link in a second set offrequency subbands.

Additionally or alternatively, the UE may receive signaling configuringthe UE to monitor a first beam-pair link on an orthogonalfrequency-division multiplexing (OFDM) symbol from the BS and monitor asecond beam-pair link on the OFDM symbol from a second BS.

At 904, the UE may monitor at least two beam-pair links for downlinkcontrol channel transmissions based, at least in part, on the receivedsignaling.

At 906, the UE may transmit feedback to the BS based, at least in part,on the monitored beam-pair links.

According to aspects, the UE may transmit the feedback to the BS bydetermining a channel strength associated with one or more monitoredbeam-pair links, and transmitting the channel strength of the beam-pairlinks to the BS.

As described above, the UE may be configured to monitor a first downlinkreference signal transmitted using a first antenna port using a firstbeam-pair link and monitor a second downlink reference signaltransmitted using a second antenna port using a second beam-pair link.The UE may determine a signal strength associated with the firstdownlink reference exceeds a signal strength associated with the seconddownlink reference signal. In response, the UE may transmit feedback tothe BS using the first beam-pair link.

Based, at least in part, on the feedback, the UE may receive a controlchannel transmission using a first beam-pair link in a slot, wherein thecontrol channel transmission indicates a change in the transmit beam tobe used by the BS to transmit a downlink shared channel. The UE maychange the receive beam used based on the change in the transmit beam.Thereafter, the UE may receive the downlink shared channel transmissionusing the changed receive beam.

The UE may transmit a confirmation of the transmit beam change. Theconfirmation may be an explicit acknowledgement. The confirmation may bean explicit acknowledgement or may be implicit via an acknowledgement ornegative acknowledgement associated with a PDSCH.

According to aspects, the UE may receive the downlink shared channeltransmission in a later slot. According to aspects, the UE may receivethe downlink shared channel transmission in the same slot.

As described above, the UE may be configured to monitor a first numberof control beams configured to transmit control channel transmissions,and a second number of data beams configured to transmit data channeltransmissions. The control beams may each map to one data beam (e.g., asdescribed in Mode 1) or two control beams may map to a single data beam(e.g., as described in Mode 2).

FIG. 10 illustrates example operations 1000 which may be performed by aBS (TRP) 110 having one or more components as illustrated in FIG. 4, inan effort to support a UE monitoring multiple beam-pair links for adownlink control channel transmission.

At 1002, the BS may transmit signaling configuring a UE to operate in atleast one of a set of different modes of monitoring beam-pair links,wherein each beam-pair link comprises a transmit beam configured to beused by the BS for beamformed transmissions and a corresponding receivebeam used by the UE. At 1004, the BS may transmit downlink controlchannel transmissions to the UE using at least two beam-pair links. At1006, the BS may receive feedback from the UE based, at least in part,on the monitored beam-pair links. At 1008, the BS may communicate withthe UE based, at least in part, on the received feedback.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software/firmwarecomponent(s) and/or module(s), including, but not limited to a circuit,an application specific integrated circuit (ASIC), or processor.Generally, where there are operations illustrated in figures, thoseoperations may have corresponding counterpart means-plus-functioncomponents.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software/firmwarecomponent(s) and/or module(s), including, but not limited to a circuit,an application specific integrated circuit (ASIC), or processor.Generally, where there are operations illustrated in Figures, thoseoperations may be performed by any suitable corresponding counterpartmeans-plus-function components. As an example, one or more of thecomponents of the BS 110 and the UE 120 illustrated in FIG. 4 may beconfigured to perform means corresponding to the (method) stepsdescribed herein. For example, the antenna 434, mod/demod 432, anycombination of the processors 420, 430, and 438, the andcontroller/processor 440 may be configured to perform means fortransmitting, means for receiving, means for communicating, and meansfor configuring. As another example, the antenna 452, mod/demod 454, anycombination of the processors 458, 464, 466, and thecontroller/processor 480 may be configured to perform means forreceiving, means for monitoring, means for transmitting, means formonitoring, means for determining, means for changing, and means forconfiguring.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or combinations thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, software/firmware, or combinations thereof. To clearlyillustrate this interchangeability of hardware and software/firmware,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware orsoftware/firmware depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in asoftware/firmware module executed by a processor, or in a combinationthereof. A software/firmware module may reside in RAM memory, flashmemory, ROM memory, EPROM memory, EEPROM memory, phase change memory,registers, hard disk, a removable disk, a CD-ROM, or any other form ofstorage medium known in the art. An exemplary storage medium is coupledto the processor such that the processor can read information from, andwrite information to, the storage medium. In the alternative, thestorage medium may be integral to the processor. The processor and thestorage medium may reside in an ASIC. The ASIC may reside in a userterminal. In the alternative, the processor and the storage medium mayreside as discrete components in a user terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software/firmware, or combinations thereof. Ifimplemented in software/firmware, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD/DVD or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software/firmware is transmitted from awebsite, server, or other remote source using a coaxial cable, fiberoptic cable, twisted pair, digital subscriber line (DSL), or wirelesstechnologies such as infrared, radio, and microwave, then the coaxialcable, fiber optic cable, twisted pair, DSL, or wireless technologiessuch as infrared, radio, and microwave are included in the definition ofmedium. Disk and disc, as used herein, includes compact disc (CD), laserdisc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for wireless communication by a userequipment (UE), comprising: receiving signaling configuring the UE tooperate in at least one of a set of different modes of monitoringbeam-pair links, wherein each beam-pair link comprises a transmit beamconfigured to be used by a base station (BS) for beamformedtransmissions and a corresponding receive beam used by the UE, andwherein the signaling further configures the UE to monitor at least twobeam-pair links for downlink control channel transmissions based on aslot-based hopping pattern; monitoring the at least two beam-pair linksfor the downlink control channel transmissions based, at least in part,on the received signaling and in accordance with the slot-based hoppingpattern; and transmitting feedback to the BS based, at least in part, onthe monitored beam-pair links, wherein transmitting the feedbackcomprises: determining a channel strength associated with one or moremonitored beam-pair links; and transmitting the channel strength to theBS as part of the feedback.
 2. The method of claim 1, wherein monitoringthe at least two beam-pair links further comprises: monitoring adownlink shared channel using a same beam-pair link as the downlinkcontrol channel.
 3. The method of claim 1, wherein receiving thesignaling configuring the UE to operate in at least one of a set of thedifferent modes comprises: receiving signaling configuring the UE tomonitor a first beam-pair link in a first orthogonal frequency-divisionmultiplexing (OFDM) symbol and to monitor a second beam-pair link in asecond OFDM symbol.
 4. The method of claim 1, wherein receiving thesignaling configuring the UE to operate in at least one of a set of thedifferent modes comprises: receiving signaling configuring the UE tomonitor a first beam-pair link in a first set of frequency subbands andto monitor a second beam-pair link in a second set of frequencysubbands.
 5. The method of claim 1, wherein receiving the signalingconfiguring the UE to operate in at least one of a set of the differentmodes comprises: receiving signaling configuring the UE to monitor afirst beam-pair link on an orthogonal frequency-division multiplexing(OFDM) symbol from the BS and monitor a second beam-pair link on theOFDM symbol from a second BS.
 6. The method of claim 1: whereinmonitoring the at least two beam-pair links comprises: monitoring afirst downlink reference signal transmitted using a first antenna portusing a first beam-pair link; monitoring a second downlink referencesignal transmitted using a second antenna port using a second beam-pairlink; and determining a signal strength associated with the firstdownlink reference exceeds a signal strength associated with the seconddownlink reference signal, and wherein transmitting the feedbackcomprises: transmitting the feedback using the first beam-pair link. 7.The method of claim 1, further comprising: based, at least in part, onthe feedback, receiving a control channel transmission using a firstbeam-pair link in a slot, wherein the control channel transmissionindicates a change in the transmit beam to be used by the BS to transmita downlink shared channel; changing the receive beam at the UE based onthe change in the transmit beam; and receiving the downlink sharedchannel transmission using the changed receive beam.
 8. The method ofclaim 7, wherein receiving the downlink shared channel transmissionusing the changed receive beam comprises: receiving the downlink sharedchannel transmission in a later slot.
 9. The method of claim 7, whereinreceiving the downlink shared channel transmission using the changedreceive beam comprises: receiving the downlink shared channeltransmission in the slot after a guard period, wherein the guard periodseparates the control channel transmission and the downlink sharedchannel transmission.
 10. The method of claim 1, wherein the signalingcomprises: configuring the UE to monitor a first number of control beamsconfigured to transmit control channel transmissions, and a secondnumber of data beams configured to transmit data channel transmissions.11. The method of claim 10, wherein two of the control beams map to asingle data beam of the data beams.
 12. The method of claim 1, furthercomprising: receiving, from the BS, a change in a transmit beamassociated with at least one beam-pair link; and transmitting aconfirmation of the change in the transmit beam.
 13. The method of claim12, wherein the confirmation is one of an explicit acknowledgment or animplicit acknowledgment associated with a downlink shared channel. 14.The method of claim 1, wherein the signaling configuring the UE tomonitor based on the slot-based hopping pattern configures the UE tomonitor using a first beam during odd numbered slots and to monitorusing a second beam during even numbered slots.
 15. The method of claim1, further comprising transmitting, to the BS, an indication of apreferred hopping pattern, wherein: monitoring the at least twobeam-pair links for the downlink control channel transmissions isperformed in accordance with the preferred hopping pattern; and thepreferred hopping pattern indicates a percentage of time for monitoringa first transmit beam and a percentage of time for monitoring a secondtransmit beam.
 16. A method for wireless communication by a base station(BS), comprising: transmitting signaling configuring a user equipment(UE) to operate in at least one of a set of different modes ofmonitoring beam-pair links, wherein each beam-pair link comprises atransmit beam configured to be used by the BS for beamformedtransmissions and a corresponding receive beam used by the UE, andwherein the signaling further configures the UE to monitor at least twobeam-pair links for downlink control channel transmissions based on aslot-based hopping pattern; transmitting downlink control channeltransmissions to the UE using at least two or more beam-pair links;receiving feedback from the UE based, at least in part, on the monitoredbeam-pair links, wherein the feedback comprises a channel strengthassociated with at least one of the beam-pair links; and communicatingwith the UE based, at least in part, on the received feedback.
 17. Themethod of claim 16, further comprising: transmitting a downlink sharedchannel using a same beam-pair link as the downlink control channel. 18.The method of claim 16, wherein transmitting the signaling configuringthe UE to operate in at least one of a set of the different modescomprises: transmitting signaling configuring the UE to monitor a firstbeam-pair link in a first orthogonal frequency-division multiplexing(OFDM) symbol and to monitor a second beam-pair link in a second OFDMsymbol.
 19. The method of claim 16, wherein transmitting the signalingconfiguring the UE to operate in at least one of a set of the differentmodes comprises: transmitting signaling configuring the UE to monitor afirst beam-pair link in a first set of frequency subbands and to monitora second beam-pair link in a second set of frequency subbands.
 20. Themethod of claim 16, wherein transmitting the signaling configuring theUE to operate in at least one of a set of the different modes comprises:transmitting signaling configuring the UE to monitor a first beam-pairlink on an orthogonal frequency-division multiplexing (OFDM) symbol fromthe BS and monitor a second beam-pair link on the OFDM symbol from asecond BS.
 21. The method of claim 16: wherein transmitting controlchannel transmissions comprises: transmitting a first downlink referencesignal using a first antenna port using a first beam-pair link; andtransmitting a second downlink reference signal using a second antennaport using a second beam-pair link, and wherein receiving the feedbackcomprises: receiving the feedback on the beam-pair link associated witha higher downlink reference signal strength.
 22. The method of claim 16,further comprising: based, at least in part, on the feedback,transmitting a control channel transmission using a first beam-pair linkin a slot, wherein the control channel transmission indicates a changein the transmit beam to be used by the BS to transmit a downlink sharedchannel; and transmitting the downlink shared channel transmission usingthe changed transmit beam.
 23. The method of claim 22, whereintransmitting the downlink shared channel transmission using the changedtransmit beam comprises: transmitting the downlink shared channeltransmission in a later slot.
 24. The method of claim 22, whereintransmitting the downlink shared channel transmission using the changedtransmit beam comprises: transmitting the downlink shared channeltransmission in the slot.
 25. The method of claim 22, furthercomprising: receiving, from the UE, confirmation of the changed transmitbeam.
 26. The method of claim 16, wherein the signaling comprises:configuring the UE to monitor a first number of control beams configuredto transmit control channel transmissions, and a second number of databeams configured to transmit data channel transmissions.
 27. The methodof claim 26, wherein two of the control beams map to a single data beamof the data beams.
 28. An apparatus for wireless communication by a userequipment (UE), comprising: at least one processor configured to:receive signaling configuring the UE to operate in at least one of a setof different modes of monitoring beam-pair links, wherein each beam-pairlink comprises a transmit beam configured to be used by a base station(BS) for beamformed transmissions and a corresponding receive beam usedby the UE, and wherein the signaling further configures the UE tomonitor at least two beam-pair links for downlink control channeltransmissions based on a slot-based hopping pattern; monitor the atleast two beam-pair links for the downlink control channel transmissionsbased, at least in part, on the received signaling and in accordancewith the slot-based hopping pattern; and transmit feedback to the BSbased, at least in part, on the monitored beam-pair links, whereintransmitting the feedback comprises: determining a channel strengthassociated with one or more monitored beam-pair links; and transmittingthe channel strength to the BS as part of the feedback; and a memorycoupled to the at least one processor.
 29. An apparatus for wirelesscommunication by a base station (BS), comprising: at least one processorconfigured to: transmit signaling configuring a user equipment (UE) tooperate in at least one of a set of different modes of monitoringbeam-pair links, wherein each beam-pair link comprises a transmit beamconfigured to be used by the BS for beamformed transmissions and acorresponding receive beam used by the UE, and wherein the signalingfurther configures the UE to monitor at least two beam-pair links fordownlink control channel transmissions based on a slot-based hoppingpattern; transmit downlink control channel transmissions to the UE usingat least two or more beam-pair links; receive feedback from the UEbased, at least in part, on the monitored beam-pair links, wherein thefeedback comprises a channel strength associated with at least one ofthe beam-pair links; and communicate with the UE based, at least inpart, on the received feedback; and a memory coupled to the at least oneprocessor.